A conventional wind turbine (see FIG. 1) comprises three blades 10 connected to a blade bearing 19 to enable rotation around a longitudinal axis of the blade 10 (a rotation commonly known as “pitch”). The blade bearing 19 is connected to a main shaft 15 which carries the rotation movement of the rotor, to which the blades 10 are connected, to a gearbox which changes the angular rotation speed, and from there to an electrical generator.
In a conventional lightning protection system, a lightning current received by a blade is transmitted to earth by the following route (see FIGS. 1 and 2):                A lightning impact received at the tip of the blade is conveyed by first conduction means 25, 27; 25′, 27′ located inside the blade (the conduction means 27, 27′ can be joined to a structural element 17 of the blade) to a metal band 18 located at the blade root at a certain distance from the blade bearing 19.        
A flashover takes places from the metal band 18 to a lightning current transmission element 31 and another flashover takes place from the lightning current transmission element 31 to a metal ring 12 of the nacelle 13.
The lightning current follows second conduction means 28 situated inside the nacelle 13 without passing through any delicate parts of the wind turbine, such as the control cabinet of the rotor hub 21, the bearings of the main shaft, the gearbox or the generator, and reaches a yaw ring 20 of the wind turbine.
Finally, the lightning current is conveyed from the yaw ring 20 to earth through third conduction means 26 situated inside the tower 16.
The lightning current follows this route when the blade 10 is made of fibre glass or carbon fibre, materials which provide electrical insulation to prevent the lightning current passing from the blade 10 to the blade bearing 19.
ES 2 265 776 B1 describes a lightning protection system with a lightning current transmission element 31 comprising:                a first bar of a conductor material with a first and a second end opposite respectively to the metal band 18 and to the metal ring 12 at distances ensuring a flashover between them;        a second bar of an electrical insulation material capable of withstanding a temperature generated by a flashover for supporting the first bar and comprising joining means to the hub of the wind turbine.        
The present invention is oriented to improve such system reducing, particularly, the breakdown voltage between their electrodes.